Photosynthetic organisms have been cultured to produce chemicals and biologicals of interests such as fatty acids, proteins, hydrogen gas, pigments, carbohydrates, sugars, and vitamins for use in food, feed, pharmaceuticals, nutraceuticals, fuels, and other products.
Of particular interest in recent years has been the use of microorganisms, such as microalgae and photosynthetic bacteria cultures, themselves or extracts derived from the microorganism. A number of microalgal metabolites have commercial interest as chemical compounds and have been so produced. Many have attempted to grow microalgae, typically in open ponds, long tubes, and bags with tubes between them. Others have attempted growing microalgae in enclosed tank systems, but each type of system has encountered difficulties related to control and optimization of the microalgae culture. Heterotrophic microorganisms, such as microalgae and bacteria, have also been cultured in traditional stainless steel fermenters to produce for similar chemicals and biologicals for commercial products in the same fields.
In an attempt to enhance production of a microalgae culture, a parameter of the biocultivation process has been varied in an attempt to find the optimum range for that parameter.
However, it is known that multiple parameters interact with each other within a culture to give complex relationships regarding optimal ranges for each parameter. Even a simple component, such as the culture medium under auxotrophic conditions containing no more than salts, lacks simplistic optimization. For example, Pandey et al, Journal of Algal Biomass Utilization, 1(3) p. 70-81 (2010), reports very different yields using differing proportions of salts in their culturing medium even with all other culture parameters remaining unchanged. Within the article, it is noteworthy that no single salt concentration had an optimal range that controlled yield. Even different conventional culture media resulted in doubling the yield. The media compared were all previously published for Spirulina and previously optimized for Spirulina growth, yet when compared side-by-side, dramatically different yields resulted.
Given the potential market, the need for a large-scale microalgae growth system is evident; yet, the prior art systems have had little optimization before being built. Different bioreactors present different problems and are optimized differently around the parameters which are not changeable. Open ponds suffer from problems with contamination (e.g., organics, bacteria, fungi), changing conditions throughout the day and night (e.g., temperature, sunlight, wind), and other suboptimal cultivation conditions. Many bioreactors have difficulties with sufficient light reaching the microalgae for photosynthetic activity and in controlling the conditions (e.g., temperature, pH, nitrate levels). A system relying solely on ambient light as an energy source for the microalgae is susceptible to fluctuation with seasons and even clouds, which may vary random and non-reproducible manner making comparison between different runs difficult or impossible to interpret even when the same bioreactor is used.
Therefore, there is a need in the art for a system and method of optimizing culturing parameters to increase the efficiency of microalgae cultivation.